Liquid crystal display devices are elements that display characters and images using electro-optical characteristics of liquid crystal molecules, and are widely used for products such as cell phones, laptops, and liquid crystal display televisions. The liquid crystal display devices usually include a liquid crystal panel having polarizing plates (a front polarizing plate and a back polarizing plate) sandwiching a liquid crystal cell. For example, a normally black type liquid crystal display device can display a black image when no voltage is applied. In recent years, along with a higher-resolution and more versatile applications of the liquid crystal display devices, there is a demand for a liquid crystal panel having a higher contrast ratio, which can more clearly display characters and images.
Examples of conventional methods for enhancing the front contrast ratio of a liquid crystal panel include a method for reducing scattering components inside a liquid crystal cell and a method for decreasing the transmittance of a polarizing plate and increasing the degree of polarization. The method for reducing scattering components inside a liquid crystal cell is not easily applicable because it requires a design change of the cell structure and the like. In contrast, the method for decreasing the transmittance of a polarizing plate and increasing the degree of polarization is known as a method that can relatively easily enhance the front contrast ratio because the method is applicable simply by changing production conditions of the polarizing plate.
For example, as a technique to enhance the front contrast ratio, there is disclosed a liquid crystal panel having a liquid crystal cell, a first polarizing plate disposed on one side of the liquid crystal cell, and a second polarizing plate disposed on the other side of the liquid crystal cell, wherein the second polarizing plate has a higher transmittance than the first polarizing plate (for example, see Patent Literature 1 to 5).
In regard to a technique to adjust the transmittance of a pair of polarizing plates, there is disclosed a liquid crystal panel that at least includes a liquid crystal cell, a first polarizing plate disposed on one side of the liquid crystal cell, and a second polarizing plate disposed on the other side of the liquid crystal cell, wherein the first polarizing plate includes a first polarizer and a first retardation layer disposed on the first polarizer on the side facing the liquid crystal cell; the second polarizing plate includes a second polarizer and a second retardation layer disposed on the second polarizer on the side facing the liquid crystal cell; the index ellipsoid of the first retardation layer satisfies a relationship of nx>ny≧nz; the index ellipsoid of the second retardation layer satisfies a relationship of nx=ny>nz; and a transmittance (T1) of the first polarizing plate is higher than a transmittance (T2) of the second polarizing plate (for example, see Patent Literature 6).
Further, liquid crystal display devices provided with, in addition to the polarizing plates, a brightness enhancement film, a wire grid polarizer, and the like as optical elements having polarization characteristics have been developed. More specifically, in regard to a liquid crystal display device provided with a wire grid polarizer and the like, there is disclosed a liquid crystal display device provided with a wire grid-type polarization optical element, wherein the polarization optical element has a structure including an anisotropically-shaped metal part and a dielectric part, the structure being obtained by forming a metal membrane on a transparent, flexible substrate and stretching the substrate and the metal membrane at a temperature below the melting point of the metal membrane; and the length in a shorter direction of the structure is shorter than the wavelength of light, and the length in a longer direction of the structure is longer than the wavelength of light (for example, see Patent Literature 7).